1. Field of the Invention
The present invention relates to three-dimensional (virtualized) sound. More particularly, the present invention relates to controllers for generating and rendering three-dimensional (3D) sound messages capable of playback on a variety of instruments and synthesizers.
2. Description of the Related Art
The Musical Instrument Digital Interface (MIDI) standard has been accepted throughout the professional music community as a standard set of messages for the real-time control of musical instrument performances. MIDI has become a standard in the PC multimedia industry as well.
The General MIDI standard was an attempt to define the available instruments in a MIDI composition in such a way that composers could produce songs and have a reasonable expectation that the music would be acceptably reproduced on a variety of synthesis platforms.
When a musician presses a key on a MIDI musical instrument keyboard containing or communicating to a rendering music synthesizer, the following process is initiated. The key depression is encoded as a key number and “velocity” occurring at a particular instant in time on one of 16 MIDI channels. The MIDI channel associates the key depression with a specific MIDI musical instrument keyboard. A MIDI channel is separate and distinct from an audio channel and the two should not be confused. In addition, there are a variety of other parameters which determine the nature of the sound produced. For example, each MIDI channel may have assigned a variety of parameters in the form of MIDI “continuous controllers” that alter the sound in some manner. The final result of this process is that the rendering synthesizer produces a mono or stereo sound.
Legacy MIDI currently specifies stereo playback of an instrument by specifying a pan parameter to designate the balance or mixing between the right and left streams of the stereo signal to help position the sound source between two speakers. While legacy MIDI provides a one-dimensional control for the placement of the sound source, the legacy format is incapable of placing the sound source in a three-dimensional field.
Three-dimensional sound is defined as audio that the listener perceives as emanating from locations in their surrounding space. Three-dimensional sound has been widely used in producing and rendering compelling audio content for modern Interactive Audio systems, particularly video game audio on personal computers. Modern economical audio processors have the processing power that was once previously only available in very large systems. In response, it now has become more feasible to render such 3D content in small embedded systems, such as stand-alone synthesizers or mobile telephones. With the proliferation of multi-channel systems for home-cinema, video games and music, the need is increasing for multi-channel production systems to address these new playback configurations. Since modern Interactive Audio rendering systems have more processing power than ever before, it has become more feasible to tightly integrate the functionality of music synthesis and interactive 3D positional audio.
Recognizing the latent emphasis on three-dimensional sound, the advancement of music messaging formats from a simple stereo rendition to three-dimensional sound rendition is also desirable. For example, it would be desirable to convert a composition expressed in a standard (legacy) MIDI format capable of rendering in stereo to one capable of true three-dimensional sound rendering.